Simple synthesis of ultra-high quality In$_{2}$S$_{3}$ thin films on InAs substrates*

We report a simple and reliable technique to synthesize high-quality In$_{2}$S$_{3}$ films on device-ready substrate, such as InAs substrates for useful device applications, by using thermal sulfurization in a hot-wall tube furnace. The crystal structure and composition were studied by using X-ray diffraction and energy dispersive X-ray, and the results confirmed that the synthesized In$_{2}$S$_{3}$ films were cubic $\beta $-In$_{2}$S$_{3}$ or tetragonal $\beta $-In$_{2}$S$_{3}$, depending on growth conditions. Morphology, vibrational modes, and optical properties were investigated by using field emission scanning electron microscopy, Raman, and photoluminescence spectroscopy, and the results indicated that the In$_{2}$S$_{3}$ films are remarkable crystal quality with substantial efficiency in photoluminescence. Especially, by optimizing the growth conditions, we have grown an extremely high-quality tetragonal $\beta $-In$_{2}$S$_{3}$ thin film firmly remained on the InAs substrate, for the first time.